1. Field of the Invention
The present invention relates to a process and apparatus for continuously manufacturing a molding having a number of spaces closed at the top and open at the bottom.
2. Description of the Related Art
Conventional processes and apparatus for manufacturing honeycomb moldings which are open at the top include general injection molding processes and apparatus. The operation of processes and apparatus of this type is well known, simple, and follows a set procedure. These processes and apparatus make it possible to manufacture moldings reliably.
In some circumstances, there may be a need to manufacture large quantities of moldings relatively inexpensively in a very short period. In other words, the quantity, the delivery deadline, or the costs may take priority over the accuracy of the molding shape and size. In this case, it is difficult to manufacture moldings by the conventional processes and apparatus, and it is, therefore, necessary to consider the use of a mass production system for producing the moldings.
By way of example, a molding of the type which needs to be produced relatively cheaply in a very short period of time is a lawn protector. Lawn protectors have been receiving attention for some time. Lawn protectors are laid on a lawn parking lot. Cars can be parked on the protectors so that their tires do not press on the lawn directly. This protects the lawn and does not prevent it from growing. FIG. 2 of the accompanying drawings shows part of a honeycomb molding A, which is a lawn protector.
The need to manufacture a mass of such honeycomb moldings at high speed takes priority over the need to improve the accuracy of their shape and size. It is difficult to manufacture such moldings at high speed with the conventional injection molding systems. In order for a process or an apparatus to manufacture honeycomb moldings at high speed, it is necessary to introduce a continuous manufacturing system, which may be an extrusion molding system, in place of a conventional injection system.
It is an object of the invention to provide a process and an apparatus for automatically and continuously producing a mass of moldings without the disadvantages arising in the establishment of a mass production system using the conventional apparatus of injection molding systems. This is accomplished through a continuous manufacturing system using a solid solution extrusion system having a circulation system with molds.
In accordance with an aspect of the invention, a process is provided for manufacturing a continuous molding by injecting a solid solution in order of precedence into a plurality of molds circulating in a line along an endless track, and by solidifying the injected solution. The track includes a forward path and a backward path. The backward path extends substantially horizontally or slopes down under the forward path. The front end of the forward path is positioned just under the front end of the backward path. The rear end of the forward path is positioned just under the rear end of the backward path. The continuous molding consists of a number of moldings connected end to end by a molded top plate. The moldings are open at their bottoms. The process comprises the steps of:
injecting the solution into each of the molds moving along the forward path;
removing the continuous molding from each of the molds by displacing the mold down, little by little in order of precedence from the molding in close contact with the mold while the injected solution is solidifying;
moving from the front end of the forward path down to the front end of the backward path, the mold released from the removing step;
returning the mold along the backward path; and
lifting the mold from the rear end of the backward path to the rear end of the forward path.
By injecting a solid solution from an extrusion type injector into the molds in order of precedence, this process can continuously manufacture a continuous molding consisting of a number of moldings open at the bottoms and connected end to end by a top plate, molded at the same time. As a result, it is possible to realize a mass production system, which can greatly lower the molding production costs.
In accordance with another aspect of the invention, an apparatus is provided for manufacturing a continuous molding continuously by injecting a solid solution in order of precedence into a plurality of molds circulating in a line along an endless track, and by solidifying the injected solution. Each of the molds includes a plurality of pins which can protrude up into cavities in the mold. The continuous molding consists of a number of moldings connected end to end by a molded top plate. The moldings are open at the bottoms. The apparatus includes:
conveying means for horizontally conveying the molds in close contact and in series along the track;
injecting means for injecting the solution into each of the molds moving forward along the track, the injecting means being positioned above the starting point where the conveying means starts conveying the molds;
a pressurizer for pressing the upper surface of the injected solution with a predetermined pressure to make the surface continuously flat, the pressurizer being positioned adjacently to and downstream from the injecting means;
guide means for guiding the molds gradually down by using the conveying force;
removing means for protruding the pins up as the molds are moving down; and
circulating means for circulating to the starting point the molds removed from the molding.
This apparatus can implement the foregoing process securely. The apparatus includes molds of the same shape. By circulating the molds, the apparatus can make a molding continuously. This makes the molding production costs relatively low. While the guide means is moving each of the molds gradually down, the pins protrude up into the cavities in the mold to remove the molding already cooled and solidified in the mold. This makes the removal secure.
It is preferable that each of the molds include guide rollers which can be guided by the guide means in such a manner that, while the mold is moving forward along the guide means and gradually down out of close contact with the molding, the mold is kept horizontal. This enables the locus of the mold moving during the removing step to be limited to the horizontal (direction) by the synthesis of the substantially horizontal movement and vertical movement of the mold. The position of the mold can, therefore, be kept always horizontal, although it tends to tilt.
If a mold tilted when the injected solution in it has not completely solidified, the upper surface of the solution might start solidifying while it is not horizontal. This makes the molding bad in shape. If an inclined mold were removed down from the molding, the mold surfaces sliding on the adjacent molds would not be vertical. This prevents the removal from being smooth. It is very easy to solve these problems by keeping the molds individually horizontal while the molds are removed from the molding.
It is preferable that the apparatus further include means for urging forward and backward into close contact at least two of the molds moving during a period of a molding step in which the molds move forward while the solution is injected into the molds.
When the solution is injected into each of the molds during the period of the molding step, the injection pressure might otherwise separate adjacent molds. This defines gaps between the molds, through which the solution may leak out. By limiting the period during which the solution is injected, and by urging the molds forward and backward into close contact, it is possible to keep the solution from leaking out through the gaps. It is therefore possible to inject the solution safely and securely.
It is preferable that the apparatus further include means for urging forward the rear end of the mold having circulated and returned to the starting point, and for urging backward the front end of the mold at the end of the forward mold movement. This urging means brings all the molds in the molding step into close contact. This makes it possible to keep the apparatus operating without preventing the molds from moving down smoothly from the molding, and from returning smoothly to the starting point of the production.
Each of the molds may include a formwork, an intermediate plate and a movable plate. The formwork has the cavities corresponding to the molding. The intermediate plate closes the lower side of the formwork and has pin holes. Each of the pins extends through one of the holes in such a manner that the pins can protrude from the holes into the cavities. The pins are embedded in the movable plate in such a manner that they extend toward the intermediate plate. The movable plate can move toward and away from the intermediate plate within a predetermined range. Otherwise, the formwork and the intermediate plate might be integral. In this case, the molds are simple in structure. The movable plate can move toward and away from the intermediate plate within the predetermined range. The pins can protrude into the cavities. It is therefore easy to handle the molds and take the molding off them.
Each of the molds may include inner rollers supported on both sides of a front portion thereof and outer rollers supported on both sides of a rear portion thereof. The apparatus may further include inner and outer guide rails for guiding the inner and outer rollers, respectively, to keep the molds horizontal and move the molds forward and gradually down. The apparatus may also include a rail and a holding roller for stopping the movable plate from moving down. One of the rail and the roller is supported by the lower side of the movable plate or along and below the guide rails. The other of the rail and the roller is supported along and below the guide rails or by the lower side of the movable plate.
While each of the molds is moved forward with its movable plate stopped from moving down by the cooperation of the holding roller and the rail, the formwork and the intermediate plate move down at the same time along the guide rails. This protrudes the pins gradually into the cavities, taking the molding off the mold.
The apparatus may further include:
a first lift for moving up and down at the end point of the forward path to move down each of the molds;
guide tracks extending in parallel to the forward path horizontally from the point where the first lift has moved the mold down, so that the guide rollers can roll on the guide tracks;
a belt conveyor extending along the guide tracks for conveying the molds; and
a second lift for lifting each of the molds from the end points of the guide tracks to the starting point of the forward path.
The mold conveyed to the end point of the forward path can be moved down by the first lift, then conveyed backward along the horizontal guide tracks by the belt conveyor, and thereafter returned securely to the starting point of the forward path by the second lift.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming part of the disclosure. For a better understanding of the invention, its operating advantages, specific objects attained by its use, reference should be had to the drawing and descriptive matter in which there are illustrated and described preferred embodiments of the invention.